The Texan was once again coaxed throughout the day by his US Postal team-mates but finally pulled clear of his last remaining supporter, Roberto Heras, on the Plateau-de-Beille.

After his initial break Heras and Joseba Beloki briefly matched the pace before Armstrong once again lifted the tempo and pulled well clear.

Jalabert attacked once again

He passed the finishing line after six hours in the saddle a minute clear of Heras in second and Beloki third.

Raimondas Rumsas finished fourth, 1m23s behind the stage winner.

The style of Armstrong's victory was a mirror image of Thursday's attack but was earlier and more devastating as a result.

And afterwards he said: "It was more fine work from the team. What a team.

"But the Tour is never finished. There are still lots of difficult climbs, lots of hard stages and chances you can have a problem or an accident."

In contrast to the defending champion's rapid final onslaught, Friday's racing started in the tamest of fashions as the peloton set a slow pace for the opening hour of the day.

Richard Virenque led the first break but was chased down and passed by Laurent Jalabert, who was once more inspired over the tough ascents.

The CSC-Tiscali rider had narrowly missed out on victory on Thursday and, in what is his final season as a cycling professional, broke again an hour-and-a-half into racing.

Maybe, another time, Armstrong will let me go all the way

Laurent Jalabert

Initially he lacked the required support but, with Laurent Dufaux and Isidro Nozal, he arrived at the bottom of the final peak - the "without category" Plateau-de-Beille - with a three-minute advantage.

Jalabert, who moved into a commanding lead in the King of the Mountains jersey, broke away from his fellow attackers with just 13 kilometres remaining as a chasing pack of some 40 riders lifted their chase.

But that final climb proved too much, ripping apart the main field and once again resulting in Jalabert being caught, on this occasion nine kilometres from the finish.

Jalabert said: "I had decided to take risks and attack early to score points on the first four climbs and to lose a lot of time in the last climb so that maybe, another time, Armstrong will let me go all the way."

With seven kilometres to go, Heras, as on stage 11 swept Armstrong up the mountain with Beloki, before the American stretched clear.

Armstrong now leads by more than two minutes from Beloki.

Britain's David Millar had a disastrous day in the saddle, coming over the line in 142nd place and 40 minutes behind Armstrong. He is now 74th overall.